It has been common practice to provide enclosures for electrical control equipment which were typically constructed of heavy steel frame members and covered with heavy sheet metal panels which were bolted, or more likely welded, to the frame members. This resulted in heavy, expensive structures which are now being supplanted by lightweight, more economical structures. A modular approach is being taken to facilitate the use of replaceable plug-in units. For a motor control unit there now exists a lightweight framework into which a removable pan assembly is placed which includes a molded case circuit breaker. The pan assembly and circuit breaker are held in place by a pan latch which releasably holds the assembly in place. This allows the pan assembly and circuit breaker to be easily removed in the field to facilitate inspection, repair and modification.
It is common practice to provide enclosures for electrical control equipment with interlock features to permit accessibility to the interior of the enclosure by a skilled worker when desired, but to prevent inadvertent entry into the enclosure when the enclosed circuit breaker and control elements are electrically energized. An interlock is typically designed to fit one enclosure or device made by one manufacturer so that an interlock is an element which must be included when designing equipment such as a motor control center.
Typical circuit breaker operators and interlock arrangements are disclosed in U.S. Pat. No. 3,122,615 which issued on Feb. 25, 1964 to R. L. Chace and U.S. Pat. No. 4,104,491 which issued on Aug. 1, 1978 to G. R. Duble. These patents generally disclose mechanisms which are designed to fulfill the requirement that the interlock between the switching device and the door of its enclosure normally prevent operation of the switch to close its contacts when the door is open, that it be possible to defeat the interlock deliberately to close the switch contacts when the door is open, that it prevent closing of the switching device while the door is being closed until the door has been properly secured with fastening hardware, that the interlock not interfere with the proper closing of the door when the switching device is on, and that the mechanical linkage between the switching device and its operating handle be such that the handle remains in control of the device, even when the door of the enclosure is open.
These mechanisms were designed for use with prior enclosures and framework and were not designed with lightweight framework and molded-case circuit breakers in mind. These devices have many parts, some of which may require plating or machining, and are not necessarily simple in construction or operation. They are relatively complicated to use, if at all, with molded-case circuit breakers. It is therefore desirable to have a mechanism which is simple to operate and relatively inexpensive to manufacture which is useable with modern framework and molded case breakers.
Mechanisms useable with molded case breakers are disclosed in U.S. Pat. No. 3,311,720 which issued to J. E. Johnson on Mar. 28, 1967 and U.S. Pat. No. 3,358,094 which issued to R. P. Metz on Dec. 12, 1967. These disclose a breaker handle operating mechanism which mounts as a unit on a circuit breaker or switch for operating the operating handle of the circuit breaker or switch, which mechanism comprises interlocking means cooperable with an enclosure cover structure to automatically latch the cover structure closed when the circuit breaker or switch is closed and to automatically latch the circuit breaker or switch open when the enclosure cover structure is opened.
It is clear that the above structures provide several interlocking features, but none interfere with removal of the pan assembly and circuit breaker in the modern environment or prevent their inadvertent or unintentional removal under full load. It is therefore desirable to have a circuit breaker operator and interlock which prevents unintentional or inadvertent removal of the circuit breaker and prohibits removal of the breaker under load. It is also desirable to have a universal circuit breaker operator which is useable with various manufacturers' circuit breakers without major modification to the circuit breaker or the operator.
Accordingly, it is an object of the present invention to provide a universal circuit breaker operator and interlock which is simple to operate and economical to manufacture and adapts to fit most breakers. This object is achieved by using a slidably moveable assembly which does not require special machining and which has an opening for receiving the handle of a circuit breaker.
It is an object of the present invention to provide a circuit breaker operator and interlock which prohibits removal of the circuit breaker under load. This objects is achieved by providing a sliding operator mechanism which locks the pan assembly in place and prevents unintentional removal of the circuit breaker under load and prevents insertion of the breaker under load.